Oxford Partial Knee ® Microplasty ® Instrumentation Complete Cemented and Cementless Surgical Technique

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2 | Oxford Partial Knee Oxford Partial Knee Introduction Tibial Components The Oxford Partial Knee is the natural evolution of the original meniscal arthroplasty, which was first used in 1976.1 It continues to offer the advantage of a large area of contact throughout the entire range of movement for minimal polyethylene wear, as seen in the Oxford Partial Knee Phase I and II.2–4 The tibial components, also made of cast cobalt chromium molybdenum alloy, are available in seven sizes, both right and left. Their shapes are designed to provide optimal bone coverage while avoiding component overhang...

3 | Oxford Partial Knee Patient Selection There are well-defined circumstances in which the Oxford Partial Knee for medial arthroplasty is appropriate and certain criteria must be fulfilled for success: • The operation is indicated for the treatment of anteromedial osteoarthritis.4 • There must be full thickness cartilage loss on both sides of the medial compartment with bone on bone contact (Figure 1). This may be demonstrated radiographically (weight bearing A/P, Rosenberg or varus stress) or arthroscopically. The results of replacement for partial thickness cartilage loss are unpredictable.9...

4 | Oxford Partial Knee • Neither the patient's age, weight nor activity level are contraindications, nor is the presence of chondrocalcinosis.13-15 • Unicompartmental arthroplasty is contraindicated in all forms of inflammatory arthritis. (The pathological changes of early rheumatoid arthritis can be confused with those of medial compartment osteoarthritis). The high success rates that were reported for Oxford Partial Knee5,6 were achieved in patients with anteromedial osteoarthritis, and they may not be achieved with other diagnoses. The Oxford implant has also been used successfully in the...

5 | Oxford Partial Knee Preoperative X-ray Template The size of femoral component can be chosen preoperatively based on the patient’s height using X-ray templates (Figure 2). A true lateral radiograph is required to accurately template. Apply the outlines on the template to the X-ray image of the medial femoral condyle. The line along the central peg of the implant should be 10 degrees flexed compared to the long axis of the femoral shaft. The outer surface of the diagrammatic component should lie about 2 mm outside the radiographic image to allow for the thickness of articular cartilage. For...

6 | Oxford Partial Knee Open vs. Minimally Invasive Technique One advantage of unicompartmental arthroplasty is that it can be performed through a small incision without dislocating the patella, thus avoiding damage to the synovial reflections of the suprapatellar pouch. This can reduce postoperative pain and allow a more complete and rapid recovery of flexion.18 With proper use of the Oxford Partial Knee instrumentation, the operation can be performed through a small incision with great precision. However, surgeons learning the procedure can extend the soft tissue incision beyond the limits...

7 | Oxford Partial Knee Surgical Technique Inflate a thigh tourniquet and place the draped leg on a thigh support, with the hip flexed to about 30 degrees and the leg dependent. The knee must be free to flex fully and the leg should hang with the knee flexed about 110 degrees (Figure 4). The thigh support must not be placed in the popliteal fossa as this will increase the risk of damage to the popliteal vessels. With the knee flexed to 90 degrees, make a medial parapatellar skin incision from the medial margin of the patella to a point 3 cm distal to the joint line (Figure 5). Deepen the incision...

8 | Oxford Partial Knee Osteophyte Excision All osteophytes must be removed from the medial margin of the medial femoral condyle and from both margins of the intercondylar notch (Figure 6). The assistant extends and flexes the knee, moving the incision up and down, allowing the various osteophytes to come into view. Osteophytes on the tibial plateau in front of the insertion of the ACL and in the top of the notch must be removed to allow the fixed flexion deformity to correct. Osteophytes on the tibia in front of the medial compartment should be removed, but medial tibial osteophytes should not...

9 | Oxford Partial Knee Tibial Plateau Resection With the knee in flexion, insert the femoral sizing spoon centrally on the condyle (based on preoperative estimate sizing) starting with 1 mm thick spoon. With all retraction removed, assess the ligament tension. Ideally it should twist up to 20 degrees in both directions. Usually the 1 mm thick femoral sizing spoon achieves the proper ligament tension. If not, replace with the 2 or 3 mm generic sizing spoon until the proper ligament tension is achieved. The optimal size of the femoral component is confirmed by examining the relationship of the...

10 | Oxford Partial Knee Tibial Plateau Resection (cont.) Confirm the proposed level of resection is correct. The saw cut should pass 2 or 3 mm below the deepest part of the erosion, unless the erosion is very deep in which case the cut should be above the bottom of the defect. If it seems that too much bone is being removed the zero shim can be replaced by the +2 shim which will remove 2 mm less bone. Use a reciprocating saw with a stiff narrow blade to make the vertical tibial saw cut. The Oxford Saw Blade Kit contains blades with markings to indicate the depth to safely divide the posterior...

11 | Oxford Partial Knee Before making the horizontal cut, insert a medial collateral ligament (MCL) retractor. Ensure this retractor is between the saw and the MCL. Remove the 0 mm uncaptured shim from the tibial resection guide and insert the 0 mm captured shim (Figure 12 inset). This is especially important when performing a cementless procedure as the capture will help create a smooth horizontal resection. Use a 12 mm wide oscillating saw blade with appropriate markings to excise the plateau (Figure 12). Ensure the saw blade is guided along the MCL retractor to completely cut the medial cortex....